Field coil for motors



Patented Sept. 7, 1937 UNITED STATES PATENT OFFICE FIELD COIL FOR MOTORSPennsylvania Application November 28, 1936, Serial No. 113,176

2 Claims.

My invention relates to iield-coils for salientpole dynamo-electricmachines, and it has particular relation to special-configurationfield-coils for driving or traction motors for railway and motor-coachservice.

An object of the invention is to conserve the available space betweenthe armature and the eld-frame or yoke of a direct-current tractionmotor, so as to make it possible to reduce the radial extent of thisspace,gthus bringing the ,d-frame closer to the armature and reducingthe'aize and weight of the motor, while at the samtime causing thefield-coils to ilt more closely against the held-frame member so as toavoid dead-air pockets and to facilitate the transfer of heat from thecoil to the framemember.

The conservation of traction-motor weight, or the ability to obtain thesame or greater horse power out of a lighter weight of motor, is anextremely important item in all self-propelled vehicles, andparticularly invbuses such as trolley buses, where the vertical spaceavailable underneath the floor of the vehicle is limited, so that areduction in the size of the motor may make the difference between atwo-motor bus and a singlemotor bus. Furthermore, the difference betweena two-motor bus and a single-'motor bus may be that the single-motor busis so similar to a gasoline-driven bus that it may be produced on thesame -manufacturing line as a gasolinedriven bus, whereas the two-motorbus cannot be manufactured in this way because it is so special.

The particular object of my invention is to f make a field coil,utilizing wedge-shaped strapcopper ortapered copper straps, whereby the-coil as a whole nests snugly against the inner surface of thecylindrical frame-member substantially without dead-air spaces, andwhereby the coil as a whole tapers down, in cross-section, from amaximum width at its outer periphery to a minimum width at its innerperiphery, thereby more completely utilizing the available space betweenthe armature and the cylindrical framemember of the motor.

In the accompanying drawing, the single gure of which is a somewhatdiagrammatic fragmentary cross-sectional view of a motor embodying myinvention in a preferred form, the motor comprises a salient-polestator-member which is made up of a magnetizable cylindrical frame oryoke-member 2, salient magnetizable main-pole and commutating-pole,members 3 and 4, main eld coils 5, and commutating pole coils I. The

(Cl. P11-252) motor also has an armature member, the outer periphery ofwhich is indicated at 1.

According to my invention, at least some of the held-coil members,either the main fieldcoils 5 or the commutating held-coils 6, or both ofthem, are specially constructed in order to conserve space and tofacilitate heat-transfer from the coils to the cylindrical frame member2.

In the particular embodiment of my invention shown in the drawing, themain field-coils 5 are specially constructed, being wound withwedgeshaped conducting straps 8, that is, with copper straps having atapered cross-section, the wide end of the cross-section being towardthe cylindrical frame-member 2. Each of the conducting straps isprovided with a light insulation 3, so as to insulate the several turnsfrom each other, and the whole coil is provided with a thicker outsideinsulation I0 for the purpose of insulating the coil from themagnetizable frameparts 2 and 3. i

It will be perceived that the utilization of wedge-shaped conductingstraps 8 causes the outer periphery of the coil to be curved, so as tofit snugly against the inner surface of the cylindrical frame-member 2,thereby fully utilizing all of the available space, so as to reduce thesize of the motor, while at the same time avoiding the presence of adead-air space between the said outer periphery of the coil 5 and theinner periphery of the cylindrical frame-member 2, thereby facilitatingheat-transfer from the coil to the frame, and thus still furtherreducing the size of the motor for a given output.

Preferably each of the pole-pieces 3 carrying my improved field-coils isprovided with a plurality of coils i2 and i3, each coil being composedof a single layer of the wedge-shaped copper straps 8. The outer coil I2thus nests snugly against the inner surface of the cylindricalframe-member 2 as described, and the inner coil I3 rests snugly againstthe inner periphery of the outer coil, with insulation i4 therebetween.In this form of construction, the inner coil has a smaller number ofturns than the outer coil,

vbut the same size of copper strap, so that the maximum width of theinner coil will be about the same as the minimum width of the outercoil, thus causing the outer configuration of the two coils las a wholeto be a tapered or trapezoidalshaped conilguratlon, effectivelyutilizing the available space of the stator-member of the motor.Usually, the two coils will be bound together in a single unit by meansof a single encompassing outer insulating covering I0.

I claim as my invention:

1. A salient-pole stator-member for a dynamoelectric machinecharacterized by a cylindrical frame-member, salient-pole membersextending inwardly therefrom, and coils disposed on certain of thesalient-pole members, each of said coils comprising a plurality of turnsof wedgeshaped conducting straps suitably insulated from adjacent turnsand from the frame and polemembers, whereby each coil as a whole nests`snugly against the inner surface of the cylindrical frame substantiallywithout dead-air spaces.

2. A salient-pole stator member for a dynamoelectric machinecharacterized by a cylindrical frame-member, salient-pole membersextending inwardly therefrom, and coils disposed on certain of thesalient-pole members, each of said certain pole-members carrying aplurality of coils, one

coil being disposed against the inner surface of the cylindricalframe-member, and another coil being disposed vagainst the opposite sideof the first-mentioned coil, each of said coils comprising a pluralityof turns of wedge-shaped conducting straps suitably insulated fromadjacent turns and from the frame and pole-members, whereby the-rst-mentioned coil nests lsnugly against the inner surface of thecylindrical frame substantially without dead-aix` spaces, and wherebythe second-mentioned coil nests snugly against the inner side of theIrst-mentioned coil, the secondmentioned coil having a smaller number ofturns than the rst-mentioned coil whereby the available space of themotor is more eiectively utilized.

RALPH E. FERRIS.

